Wide-detector axial CT versus 4 cm detector helical CT for transcatheter aortic valve replacement: iodine dose, radiation, and image quality

Feasibility of sub-second CT angiography of the abdomen and pelvis with very low volume of contrast media, low tube voltage, and high-pitch technique, on a third-generation dual-source CT scanner

BACKGROUND

Concerns about potential risks of using contrast media in patients with chronic renal insufficiency limit the utilization of CT angiography in this population.

PURPOSE

To evaluate the feasibility of abdominopelvic CTA with very low volumes of contrast media.

MATERIAL AND METHODS

In this retrospective study, 20 patients with chronic renal insufficiency underwent high-pitch abdominopelvic (AP) CTA on a third-generation dual-source CT scanner with 30 mL of nonionic iodinated contrast. The homogeneity of intravascular attenuation at the suprarenal aorta, infrarenal aorta, and the right common iliac artery was measured. Image noise, contrast-to-noise ratio (CNR), and signal-to-noise ratio (SNR) were used to assess objective image quality. Subjective image quality was evaluated on a 5-point scale (1 = unacceptable; 5 = excellent).

RESULTS

Twelve male and eight female patients underwent CTA of the abdomen and pelvis at 80 kVp. Five CTAs also included the chest (CAP). The mean scan duration was 0.78 ± 0.19 s for AP and 0.96 ± 0.06 s for CAP CTAs. The mean ± SD of attenuation at suprarenal aorta, infrarenal aorta, and right common iliac artery were 235.1 ± 68.0, 249.2 ± 61.3, and 254.4 ± 67.7 HU, respectively. The attenuation was homogeneous across vascular levels (P = 0.06). All scans had diagnostic subjective image quality with the median (IQR) of 3.5 (1.75). CNR and SNR were homogeneous across vascular levels (P = 0.08 and P = 0.14, respectively).

CONCLUSION

Sub-second, high-pitch abdominopelvic CTA with a low volume of contrast in patients with chronic renal insufficiency is technically and clinically feasible with good diagnostic image quality and homogenous attenuation across vascular levels.

Ultra-low-dose CT-guided lung biopsy in clinic: radiation dose, accuracy, image quality, and complication rate

BACKGROUND

Computed tomography (CT)-guided percutaneous lung biopsy is usually performed by helical scanning. However, there are no studies on radiation dose, diagnostic accuracy, image quality, and complications based on axial scan mode.

PURPOSE

To determine radiation dose, accuracy, image quality, and complication rate following an ultra-low-dose (ULD) protocol for CT-guided lung biopsy in clinic.

MATERIAL AND METHODS

A total of 105 patients were enrolled to receive CT-guided lung biopsy. The use of an ULD protocol (axial scan) for CT-guided biopsy was initiated. Patients were randomly assigned to axial mode (Group A) and conventional helical mode (Group B) CT groups. 64-slice CT was performed for CT-guided pulmonary biopsy with an 18-G coaxial cutting biopsy needle. The radiation dose, accuracy, image quality, and complication rate were measured.

RESULTS

Ninety-seven patients were selected for the final phase of the study. There was no significant difference between the two groups for pulmonary nodule characteristics (P > 0.05). The mean effective dose in group A (0.077 ± 0.010 mSv) was significantly reduced relative to group B (0.653 ± 0.177 mSv, P < 0.001). There was no significant difference in accuracy, image quality, and complication rate (P > 0.050) between the two modes.

CONCLUSION

An ULD protocol for CT-guided lung nodule biopsy yields a reduction in the radiation dose without significant change in the accuracy, image quality, and complication rate relative to the conventional helical mode scan.

Clinical Applications of Wide-Detector CT Scanners for Cardiothoracic Imaging: An Update

Technical developments in multidetector computed tomography (CT) have increased the number of detector rows on the z-axis, and 16-cm wide-area-coverage CT scanners have enabled volumetric scanning of the entire heart. Beyond coronary arterial imaging, such innovations offer several advantages during clinical imaging in the cardiothoracic area. The wide-detector CT scanner markedly reduces the image acquisition time to less than 1 second for coronary CT angiography, thereby decreasing the volume of contrast material and radiation dose required for the examination. It also eliminates stair-step artifacts, allowing robust improvements in myocardial function and perfusion imaging. Additionally, new imaging techniques for the cardiothoracic area, including subtraction imaging and free-breathing scans, have been developed and further improved by using the wide-detector CT scanner. This article investigates the technical developments in wide-detector CT scanners, summarizes their clinical applications in the cardiothoracic area, and provides a review of the recent literature.

Wide-detector CT combined iterative reconstruction in pediatric low-dose scan of the paranasal sinus

BACKGROUND

Computed tomography (CT) is considered a standard modality for imaging the paranasal sinus (PS), but increasingly radiation dose is of concern, especially in children.

OBJECTIVE

This study aims to investigate the feasibility of using a 320-detector CT scanner with a 16 cm wide-detector combined with iterative reconstruction (IR) algorithm to further reduce radiation dose when scanning the PS.

METHODS

A total of 90 children who underwent CT of the PS were randomly allocated into three groups namely, (1) the experimental group using low-dose wide-detector scan (n = 30, 9±4 years); (2) low-dose helical group (n = 30, 9±4 years); and (3) pediatric conventional group (n = 30, 8±4 years). Statistical software SPSS 19.0 was used for one-way ANOVA analysis of the general data (age, BMI), image quality, and radiation dose. Multiple comparisons of data without homogeneity of variance were analyzed by Bonferroni test and Tamhane's test.

RESULTS

All patients underwent successful CT examinations. No significant differences in the general data and image quality evaluation were detected between three groups (all P values > 0.05). CTDIvol and DLP were 2.87 mGy and 32.58 mGy·cm in the experimental group, 4.92 mGy and 70.84 mGy·cm in the low-dose helical group, and 9.95 mGy and 131.83 mGy·cm in the conventional group, respectively, which were significantly different among these three groups as indicated by multiple comparisons (all P values < 0.05). In the experimental group, the effective radiation dose was 0.07 mSv, which was reduced by 76% and 56% comparing to the conventional group and the low-dose helical group, respectively.

CONCLUSIONS

The 320-detector CT scanner equipped with the wide-detector combined with IR can further reduce radiation dose, while maintaining good image quality comparing to the low-dose helical or pediatric modes.

320-row CT transcatheter aortic valve replacement planning with a single reduced contrast media bolus injection

OBJECTIVE

To reduce the iodine load required for CT Transcatheter Aortic Valve Replacement (TAVR) planning on a 320-row scanner by acquiring the two CT TAVR steps (ECG-gated aortic root CTA and non-gated aorto-ilio-femoral CTA) within a single contrast media bolus injection.

METHODS

50 consecutive patients (82.6±6.9 years; 56% female) were prospectively enrolled and underwent a TAVR planning using a 320-row CT, with ECG-gated aortic root CTA immediately followed by a non-gated aorto-iliac acquisition, all within a single bolus of 40-70mL of Iohexol 350mgI/mL. The Iodine load, image quality, SNR, CNR and radiation dose were compared using a Mann-Whitney test to that of 24 consecutive patients (84.3±4.8 years, 58% female) previously imaged on a 64-row scanner with a conventional two-step protocol.

RESULTS

Iodine load was reduced by 44%. All examinations were of diagnostic quality, with improvement of the aortic root CTA image quality (4.9±0.3 versus 4.6±0.5, p<0.01) and a non-significant decrease of the aorto-iliac CTA image quality (4.7±0.6 versus 4.9±0.3, p = 0.07). SNR and CNR were significantly improved in the aortic root CTA (14.0±5.3 and 10.4±4.5 versus 10.3±4.2 and 6.8±3.3, p<0.01 for both) and non-significantly higher in the aorto-iliac CTA (16.5±8.0 and 14.1±7.9 versus 14.7±5.5 and 12.5±5.0, p = 0.42 and p = 0.66). Total radiation dose was reduced by 32%.

CONCLUSION

320-row CT scanner enables a 44% reduction of iodine load in TAVR planning, while maintaining excellent aorto-ilio-femoral arterial enhancement and lowering radiation dose.